1. Field of the Invention
The present invention relates to a method for manufacturing highly-concentrated polyglutamic acid with the additional supply of saccharides, more specifically, to a method for manufacturing highly-concentrated polyglutamic acid with high yield, but without formation of undesirable side-products by culturing a microorganism of Bacillus sp. under a fed-batch or batch condition while saccharides are additionally supplied to the culture.
2. Description of the Related Technology
Polyglutamic acid produced by microorganism is completely biodegradable, thus, has been used as an ingredient of foods and cosmetics. Recently, researches on utilization of polyglutamic acid as medical material (see: Kishida, A. and Murakami, K. et al., J. Bioactive and Compatible Polymers, 13:271–278, 1998), functional carrier, membrane material, and electrical material are being actively undertaken in the art (see: U.S. Pat. No. 5,693,751). In line with the continued efforts to produce highly-concentrated polyglutamic acid, there have been reports on a medium composition optimized for flask or batch fermentation (see: Ko, Y. K. and Gross, R. A., Biotechnol. Bioeng., 57:430–437, 1998) and an effective medium supplemented with citrate for fed-batch fermentation (see: Korean Patent No. 250627), which are, however, proven to be less satisfactory in a sense that glycerol and citrate contained in the medium cannot be utilized readily as an energy source by the microorganism. Nonetheless, there is no teaching on a medium supplemented with efficient sacchrides such as glucose or fructose for the fed-batch fermentation. Since saccharides produce a good deal of ATP through the metabolic pathway of microorganisms, they are good energy sources for the process consuming a lot of ATP such as synthetic pathway of polyglutamic acid (see: Troy F. A., J. Biol. Chem., 248:305–315, 1973).
Therefore, there is a continuing need to develop fermentation techniques to increase yield of polyglutamic acid by the efficient supply of saccharides readily available to microorganisms.